The present invention relates to a system having a signal source for generating a signal having prescribed, time varying frequency and a signal utilization device, responsive to the aforementioned signal, which carries out a useful process in dependence upon the frequency of the signal.
As an example of such a system, the signal source may comprise a voltage controlled oscillator which is responsive to a time-varying input signal S.sub.o (t) to generate an output signal having the prescribed, time varying frequency f(t) that is substantially directly proportional upon the input signal. The signal utilization means may be a laser scanner which employs an acoustic optic modulator to deflect the laser beam by an angle which is proportional to the frequency of an applied signal. As another example, the signal utilization device may comprise an interrogator-transponder system that transmits an interrogation signal having a frequency which is ramped substantially linearly upward and/or downward within a prescribed frequency range.
In systems of the type described above which are responsive to a monotonically increasing or decreasing frequency, non-linearities in this frequency with respect to time, or non-linearities in this frequency with respect to another signal or voltage introduces errors in the signal utilization device. Prior attempts to compensate for non-linearities were primarily concerned with methods and means for linearizing the time or voltage versus frequency function itself. Thus, for example, feedback loops have been provided between the output of the signal source and its control input for correcting non-linearities in the output.